Kiln



Mrch 2s, 1933. LLADD' 1,903,117

KILN A Filed Sept. 28, 1931 5 Sheets-Sheet l Q ge) b 9 t?, QS

March 28, 1933.

L. L. LADD K'ILN Filed Sept. 28, 1931 `5 Sheets-Sheet 2 March 28, 1933.

L. L. LADD KILN Filed sept. 28, 1931 5 sheets-sheet 4 L. L. LADD M arch 28, 1933.

KILN

Filed sept. 28, 1931 5 sheets-'sheet 5 Patented Mar. l28, 1933 UNITED STAT-Es PATENT oFFlcr.

LESTER L. Lann, or Locxroar, rumors man Application' led September 28, 1931. Serial No. 565.501.

This invention relates to tunnel kilns particularly adapted for use in lfiring ceramic products. Tunnel kilns` may be of the straight type, in which the ware travels on' trucks or cars; or of the circular type, in which the ware travels through the kiln on a circular conveyer, such as illustrated in my eo-pending application Serial No. 366,959, filed May 29, 1929 which has become Patent w 1,842,411. This invention is primarily intended for use in a circular tunnel kiln` although it may be applied to the straight type.

Tunnel kilns are further classified as mufiie kilns and open kilns. In the Inutile type J of kiln, a refractory wall is positioned between the ware and thefiring chamber to prevent the gases of combustion from reaching the ware. In the open type of kiln, the

combustion gases are discharged directly into s Z9 the center of the kiln in contact with the ware.

The open type of kiln is highly efficient but for` certain types of ware it is objection-V H able because the gases of combustion injure w the ware. The muiiie type of kiln is safer but not so eiiicient as an open kiln'.

Certain types of ceramic products, such as dishes and other table ware are subjected to three distinct firing operations. The bisque is first hardened in a bisque kiln and, after being hardened, it is then glazed and the glost ware is .then fired in a glost kiln. The glost Ware may then be decorated and fired in a decorating kiln. l

" Bisque kilns are usually operated at apeak temperature of 2200 F., and are of the open type because the bisque is usually not injured by combustion gases. vvGrlost kilns are operated usually at a ak temperature of o 2000 F., and decorating kilns'at 1400 F.

` Glost ware should never be'red in a kiln of.

the open type because the glaze is apt to be injured by the gases of incomplete combus tion. v e J Alltypes of tunnel kilns have a reheating zone, a firin zone, and a coo ing zone, through whic the ware travels successively. In all of the tunnel kilns heretofore in common use, the ware has been gradually heated to the peak temperature and then gradually cooled. With such kilns, therefore, it was necessary to provide a tunnel of considerable length. In the preheating zone, *ity is necessary to gradually raise the temperature u of the ware up to the fusion point to prevent 5i. cracking but, vafter the fusion point is reached, the temperature of the ware may be quickly raised to the peak temperature without cracking the goods. After the ware leaves the tiring zone it may be quickly cooled C3 to the fusion point and should then be cooled! more gradually. The ability to thus quickly heat and cool the ware has not been possible withany of the kilns heretofore in common use. C3

I The main objects of this invention are to provide'a kiln ofsemi-mulile type which appreaches the efliciency of an open kiln without permitting the objectionable gasesof incomplete combustion to contact with the ware in the firing zone; to provide a kiln of this kind having an improved form 'of tunnel; to provide a tunnel kiln having improved means for controlling the tempera- F ture in the preheating zone whereby the tem- 5 perature of the ware may be gradually raised to the fusion point and then quickly raised to thew peak; to provide improved means for controlling the temperatures in the cooling zone whereby the ware may be quickly cooled to the fusion point and then gradually cooled; and to provide a kiln of this kind which may be used as a bisque kiln, glost kiln, or decorating kiln.

,y An illustrativeembodiment of this invention is shown in the accompanying drawin?, wherein:

igure 1 is a horizontal section of a circular kiln to` which this invention is applied, the conveyer being omitted.-

Figures 2, 3, 4, 5 and 6 are enlar transverse vertical sections taken on the ines 2--2, 3-3, 4 4, 5-5 and 66, respectively, of Figure 1. l

Figs. 2 and 3 show different portions of 95 the preheating zone; Fig. 4 shows the firing zone; and Figs. 5 and 6 show dierent portions of the cooling zone.

Fig. 7 is -a top planof one Iof the @its 10o which supports the conveyer. v

cated between the air chamber and `the warev passage of the preheating zone.

Fig. 10 is an elevation lshowing tlie wall at the inlet end of the tunnel, part of the supporting structure being shown in section, and some of the delectors being omitted.

. Fig. 11 is a top plan of the same.

Fig. 12 is an elevation showing the outlet end of the tunnel. 4

In the construction illustrated, the lciln is of the circular type and comprises a fabricated metal frame structure 1, `which supports an arcuate tunnel 2 having' a central passage 3, through which the ceramic ware is slowly conveyed by means ot an annular conveyor mechanism a.

The frame structure 1 may be built on a suitable concrete foundation, not shown. ln the form shown, the frame comprises a plurality of vertically disposed angle bars 5 and 6, which are connected to horizontal bars l and 8. The upper ends of the bars 5 are secured against spreading by horizontal tie rods 9, which are disposed above the tunnel.

The tunnel 2 is supported on a pair of concrete door slabs 10 disposed on respectively opposite sides of the conveyor. Formed at the inner edges of these floor slabs, are troughs l1 which are filled with sand or other suitable sealing material to prevent the heat in the ware passage from reaching the bearings of the conveyer. Metalshields 12 form the inner walls of the troughs 11.

The tunnel comprises side walls 13 and a 'roof 14 which vary in cross section at different zones of the kiln, as shownin Figures 2 to 6, inclusive. surround the ware passage and are made o various heat resisting materials such as brick, fire brick, tile, refractory, infusorial earth, and similar materials.

In the construction shown, the tunnel defines an intermediate firing zone 15, a preheating zone 16 at the ware inlet end of the tunnel, and a cooling zone 17 at the ware outlet end.

Air is continuously driven through the ware passage against the travel of the ware by means of a blower 18 communicating with openings 19 in an end wall 2() at the outlet end of the tunnel.

At the ring zone, the tunnel is formed to provide a pair of combustion chambers 21 on respectively opposite sides of the ware passage. rilhe outer walls of these combustion chambers are `provided with fuel inlets 22 for a plurality of nozzles 23 which are connected to the usual manifolds 24 of the fuel supply.

l The inner walls of the combustion chambers 21 consist of imperforate mules 25,

`the tunnel to permit them to be readily These side walls and roof f moana` which arev arranged to prevent any of the gases of combustion from reaching the ware passage in the firing zone. These momes are seated in grooves 25.1 in the roof and floor of inserted and removed.

Located between the mue walls 25 and the Afuel nozzles, are perforated refractory walls 26 adapted to break up the flames and to assist in evenly distributing the heat.

ln order to assist in preheating the Ware before it reaches the firing zone, the combustion chambers 21 extend partly into the preheating zone, as shown in Figure 1, for conducting the combustion gases into the preheating Zone. The inutile walls 25 are coextensive with the combustion chambers so as to prevent the combustion gases from reaching the ware which has been heated above the fusion point. At the place where the combustion gases enter the Ware passage of the preheating zone, the ware has not yet been heated suciently to be discolored by the gasesa Also formed in the walls of the tunnel in thel preheating Zone, are air chambers 27 which are alined with the combustion chambers 2l. to provide communication between the combustion chambers and the ware 'passage. The inner walls of these air chambers consist of perforated partitions 28 built of bricks arranged in the manner shown in Fig. 9. With this improved construction, the combustion gases enter the ware passage at various points along the partitions 28 and mingle with the air which is blown through the tunnel by the blower 18.

Formed in the tunnel walls at respectively opposite sides of the preheating zone, are exhaust fines 29 communicating with the ware passage 3 and air chambers 27 of the preheating zone, through passages 30 and 3l, respectively. The exhaust fines 29 have outlet passages 32 leading to an exhaust tan 33, whereby air and combustion gases may be `withdrawn from the preheating zone for controlling the temperatures within this zone. The branch passages 3Q and 3l are provided with dempers 34 and 35, respectively, for regulating the amount of air and gases withdrawn at different points along the preheating zone.

ln order to prevent the exhaust fan 33 from sucking air through the ware inlet end of the tunnel a blo-Wer 36 is arranged to discharge heated air into air chambers 3'( locat-l ed adjacent this end of the tunnel. Some of this heated incoming air passes through openings 38 in an end wall 39. This end wall is provided with delectors 40 arranged to direct some of the hotair to the center of the conveyer. Dampers 41 control the amount of air passing through these openings. With this improved construction it is possible to prevent any appreciable iiow oi liti inner end of the coolin air through the ware inlet opening of the tunnel. l

Warm air from the cooling zone is conducted to the blower 36 through a ipe 42. Fresh air for further regulating t e temperature of the preheating zone may be admitted to the pipe 42 through an opening 43, which is controlled by a damper 44.

The pipe 42 receives its Warm air from air chambers 45 formed in the tunnel walls at the zone. The ixmer walls of these air cham ers consist of iml perforate bellies 46, which are arranged to prevent the blower 36 from causing the air 1n the ware passage toreverse its iiow. These baies 46 are loosely mounted in grooves 46.1 formed in the roof and floor of the tunnel.v If these bales were not used, the air in the ware passage of the firing zone would be drawn throughthe pipe 42'. The outer ends of the air chambers 45 communicate with the -ware passage through openings 47 as shown in Fig. 1, so as to Areceive some of the air which is forced into the tunnel by the blower 18. Cool air may be admitted to these air chambers through flues 48 for controlling the temperatures of the ware passage in the cooling zone. dampers 49. v

Sight openings 50 may be formed in the tunnelwalls at the inlet end of the cooling zone to permit. the operatorl to inspect the ware comingfron the firing zone.

' The ware' passage 3 at the outlet endA of the cooling zone is enlargedad] acent its upper end, as shown in Fig. 6, so vas to permit the warm air to freely rise.

The annular conveyer 4 is preferably of the general type shown in my copending application, Serial No. 366,959, vfiled May 29, 1929. In the form herein shown, it includes an annular sectional refractory platform 51 havaprons 52 dipping into the troughs 11'.

e I-beam 53, to which it is secured b brackets 54.- The lower face of the I-beam as an annular rail 55 which is supported on a plurality of wheels 5 6, arranged at intervals.

The wheels .56 have horizontal axles 57 journaled in bearin 58 which are vertically adjustable on threa ed posts 59. Also mount-` ed on the bearings 58 are guide rollers 60 for engaging the sides of the rail 55. The posts 59 are supported on blocks 61 which may be secured to the frame members 6. Two of the supporting wheels are driven by a driving mechanism including a motor 62 and speed reducer 63 geared to a air of drive shafts 64.

lThe outer ends of the rive shafts are geared to the axles of the drive wheels by' gears and 66.

The open section of the kiln, which constitutes the loading and unloading zone, has an arcuate foundation 67.

In operation, the conveyor 4 moves con- These lues are provided with platform is supported on an annular tinuously and itis loaded andunloaded in the open zone of the kiln. The conveye:

travels in the direction of the arrow shown in Figure 1 for movin the ware successively through the preheating zone 16, firing zone 1 5 and coolingl zone 17. The blower 18 causes a continuous How of air through the ware passa e against `the travel of the ware. The com ustion gases in thel combustion' chambers 21, ow into the air chambers 27 and then pass through the perforated partitions 28 into the ware passage 3 of the preheating zone, where they mingle with the air which 1s bein forced through the ware passage by the b ower 18.

The warm air and combustion gases are withdrawn from the preheating zone by the exhaust fan 33 through the passages 30 and 31 and ilues 29. The temperatures within the preheating zone may be controlled by means of the dampers 34 and 35 so as to obtain the desired gradual heating of the ware in that ortion of the preheating zone where the ware 1s in contact with the combustion gases.

Additional warm air is conducted from the air chambers 45 of the cooling zone through the ipe 42 and blower 36 to the inlet end of t e preheating zone. This prevents the air from'being sucked through the inlet end of the tunnel by the exhaust Fan 33. The temperatures in the preheating zone may be further controlled by the damper 44 and the temperatures within the cooling chambers 45 may be controlled by the dampers 49.

With this improved construction, Ythe ware is gradually heated in the preheatin zone until the ware reaches the maille Wa ls 25. The ware then u'ickly rises in temperature until it reaches t e peak temperature in the firing zone. The peak temperature of the ware is maintained throughout the firing zone and then, when. the ware reaches the cooling zone, it is quickly cooled by the. air chambers 45. When the ware passes beyond the baille walls 46, it is cooled gradually through the remaining portion of the coolin zone. With this kiln, the ware may be re and cooled, without cracking, in a much shorter period than was possible with kilns heretofore in use. v e

Although but one specific embodiment of this invention has been herein shown andv described, it will be understood that Adetails 1. A tunnel kiln comprislng a tunnel having a central ware passage and defining a pre-p heating zone, a firing zone, and a cooling zone through which the ware travels successively, said tunnel having a combustion chamber 1n the firing zone and havin an air chamber in vthe preheating zone, sai air chamber communicatng with said combustion chamber and with said ware passage, and exhaust means communicating with said air chainber Jlor withdrawing some of the air and combustion gases from said preheating zone.

2. A tunnel kiln comprising a tunnel having a central Ware passage and defining a preheating zone, a iiring zone, and a cooling Zone through which the Ware travels successively, said tunnel having a combustion chamber 1n the firing zone and having an -air chamber in the preheating zone, said air chamber providing communication between said combustion chamber and the ware passage in said preheating zone, said tunnel having air outlet nues leading from said air chamber and having other air outlet tiues leading from the ware passage in said preheating zone, and separate dampers for independently controlling said air passages. i

3. A tunnel lriln comprising a tunnel having a central Ware passage. and deiining a l preheating zone, a iiring zone, and a cooling zone through which the ware travels successively, said tunnel having a combustion chamber in the tiring zone and having an air chamber in the preheating zone, said air chamber providing communication between said combustion chamber and the Ware passage in said preheating zone, exhaust means, said tunnel having air ues leading from said air chamber to said exhaust means and having other air ilues leading from the Ware passage in said preheating zone to said exhaust means, and separate dampers lor independently controlling said air dues.

ll. A. tunnel kiln comprising a tunnel having a central Ware passage and defining a preheating zone, a liring zone, and a cooling zone through which the ivare travels successively, said tunnel having a combustion chamber in the iiring zone communicating With the Ware passage in said preheating zone, said tunnel having a plurality of airy outlets at intervals in the preheating zone, and separate dampers for controlling said outlets independently of one another.

5. A tunnel kiln comprising a tunnel having a central Ware passage and delining a preheating zone, a ring zone, and a cooling zone through which the Ware travels successively, said tunnel having a combustion chamber in the tiring Zone communicating with the ware' passage in said preheating zone, exhaust means, said tunnel having in 'said preheating zone a plurality of outlets communicating with said exhaust means, and a plurality of damper-s for independently controlling said outlets.

(i. A tunnel kiln comprising a tunnel having a central Ware passage and dening a preheating zone, a ring zone, and a ycooling zone throu h which the ware travels successively, sai tunnel having a combustion chamber in the iring zone and having an air chamber in the preheating zone communicessively, said tunnel having a colnlfiustion chamber in the firing zone andohaving an air chamber in the preheating zone, said air chamber providing communication between said combustion chamber and the 'ware passage in said preheating zone, an exhaust Elue in the preheating zone, said tunnel having air passages providing communication betvveeen said exhaust iue and said air chamber and having other air passages providingy communication between said exhaust hue and the Ware ,passage in said preheating zone,'and a plurality of dempers for independently controlling said air passages.

8.33 tunnel .kiln comprising a tunnel having a central Ware passage and deining a preheating zone, a iring zone, and a coolingV ZoneI through `which the ware travels successively, said tunnel having a combustion chamber in the iiring zone communicating with the ware passage in said preheating Zone, means for withdrawing air and combustion gases from the Ware passage of said preheating zone, and other means for conducting heated air to the 'were passage of said reheating zone.

9. vtunnel kiln comprising a tunnel having a central ware passage and defining a preheating zone, a firing zone, and a cooling zone through which tie ware travek successively, said tunnel having a combustion chamber in the ring zone communicating with the Ware passage in said preheating zone, means for withdrawing air and combustion gases from the Ware passage of said prohosting zone, and other means for conducting air from said cooling zone to the ware passage of said preheating zone.

l0.. A. tunnel lriln comprising a tunnel having a central Ware passage and dening a preheating zone, a ring zone, and a cooling Zone through which the Ware travels successively, said tunnel having a combustion chamber in the iiring zone communicating with the Ware passage in said preheating acne, said tunnel having a plurality oil air outlets at intervals in said preheating acne, separate dempers for controlling said outlets independently oi one another, and means for conducting heated air te the Ware passage adjacent the inlet enel of said preheatzone. Y

ll. A tunnel l-tiln comprising a tunnel having a central Ware passage and dening a preheating zone, a .firing sono, and a cooling nerforate muiile wall separating said com-v ustion chamber fromA the ware passage in said tiring zone, a perforate partition between said air chamberand the ware passage of said preheating zone, and exhaust means for withdrawing air. and combustion gases from said air chamber'and from the ware passage of said reheating zone.

12. A tunnel klln comprising a tunnel having a central ware passage and defining a preheating zone, a firing zone, and a cooling zone through which the ware travels suc,- ccssively, said tunnel having a combustion chamber in the firing zone and having an air chamber in the preheating zone communicating with said combustion chamber, an imperforate mule wall separating said combustion chamber from thevware passage in said Y firing zone, a perforate partition between said air chamber and the ware passage of said preheating zone, exhaust means for withdrawing air and combustion gases from passage said 'air chamber and from the ware assage of said preheating zone, and means or conducting heated air to the ware passage adjacent the inlet endof said preheating zone.

13. A tunnel kiln comprising a tunnel havlassage and defining a preheating zone, a firing zone, and a cooling zone through which the ware travels successively, said tunnel having a combustion chamber in the firing zone, fuel jets communicating with said combustion chamber,

an imperforate muiile wall arranged between said combustion chamber and the ware passa of said firingv1 zone, and a perforate ba e located between said mule wall and a cooling zone through which the ware travels successively, said tunnel having a com-V bustion chamber in said iiring zone and having an air chamber in said preheating zone communicatin with said combustion chamber, an impe orate -muiile arranged to sepa-v said preheating zone for separating a porf tion of said air chamber from the ware passage, a' perforate partition located between the ware passage and the remaining portion l of said air chamber, said tunnel 'having an exhaust flue in said preheating zone communicating with said air chamber and with said ware passage, means for withdrawing air and combustion gases from said flue, a plurality of dampers controllin communication lbetween said flue and sai air chamber, and .other dampers controlling communication between said fine and said ware passage. 16. An annular tunnel having a central ware passage and delining a, preheating zone, a firing zone, and a` cooling zone through which the ware travels successively, said tunnel having a combustion chamber in said firin zone and having' an air chamberl in said pre eating zone communicating with said 'combustion chamber,

an imperforate muiiie arranged toseparate said combustion chamber from the ware passage, a Yperforate partition located between said air chamber and said ware passage, means for withdrawing air and combustion gases from said air chamber, a flue for conducting air from said cooling zone to said preheating zone, and means for admitting fresh air to said flue at a point between said cooling and preheating zones.

LESTER L. LADD.

said jets.

14.v An annular kiln comprising an arouate tunnel havin a central ware passage and defining a pre eating zone, a firing zone,

and a cooling zone through which the were v travels successively, said tunnel having a combustion chamber in said firing zone and having an air chamber in said preheating zone communieatin with said combustion chamber, an imper orate muille arranged to separate said combustion chamber from the ware passage said muie extending partly into said preheating zone for separating a portion of said air chamber from the ware v a perforate partition located between the ware passage and the remaining rtion of said an chamber, means for causing a ilow of -air through said ware pas-- sage and other means for withdrawing air and combustion gases from said air chamber. 15. An annular kiln comprising an arcuate tuxmel having1 a central ware passage and defining a pre eating zone. a firing zone, and.

kiln comprising an arcuate 

